Method for producing non-woven webs

ABSTRACT

A method and apparatus for producing extra wide and/or laminated non-woven webs from very thin, lightweight arrays of highly-drafted and aligned fibers. The fibers are drafted and aligned into thin webs by separate draw frames and deposited at selected points and particular angular orientation on an inclined moving belt. Deposition is made in juxtaposed side-by-side arrangement for wide webs, or one ply upon another when a laminated construction is desired. The planar angle at which each web is deposited on the receiving belt is arranged with respect to the plane of the belt so that the fibers are held under tension during the entire operation.

Jan. 30, 1973 R. C. SOKOLOWSKI' METHOD FOR PRODUCING NON-WOVEN WEBS Original Filed March 14, 1968 2 Sheets-Sheet l Jan. 30, 1973 R. c. SOKOLOWSKI METHOD FOR PRODUCING NON-WOVEN WEBS 2 Sheets-Sheet 2 Original Filed March 14, 1968 United States Patent TLS. U. 156-476 7 Claims W WM...

ABSTRACT OF THE DISCLOSURE A method and apparatus for producing extra wide and/or laminated non-woven webs from very thin, lightweight arrays of highly-drafted and aligned fibers. The fibers are drafted and aligned into thin Webs by separate draw frames and deposited at selected points and particular angular orientation on an inclined moving belt. Deposition is made in juxtaposed side-by-side arrangement for wide webs, or one ply upon another when a laminated construction is desired. The planar angle at which each web is deposited on the receiving belt is arranged with respect to the plane of the belt so that the fibers are held under tension during the entire operation.

This application is a continuation of SN. 713,092, filed Mar. 14, 1968, now abandoned.

BACKGROUND OF THE INVENTION A recent development in the non-woven fabric art has been the production of strong, light-weight fabrics by passing juxtaposed slivers through a draw frame to align and draft the fibers into a thin tenuous web and depositing that web under tension onto a moving belt or sheet previously printed with adhesive. After the adhesive is set or cured, it bonds the fibers together to form a coherent light-weight fabric. The fabric may comprise fibers and adhesive alone, in which case the fabric is stripped from the supporting sheet after the adhesive is set, or the sheet itself may be left permanently attached to the fibers by the adhesive whereby the sheet becomes an integral part of the resulting laminated fabric.

While the drafting and alignment of fibers is readily controllable to provide a highly uniform sheet when making webs of narrow width, mechanical problems multiply disproportionately as widths are increased, largely because dynamic forces generated in wider drafting rolls of relatively small diameter cause the rolls to oscillate, flex, or whip at the high speeds required for economical production.

In the drafting equipment normally used in the process, pairs of aligned top and bottom fluted drafting rolls are arranged to provide light pressure nips through which juxtaposed slivers of staple length synthetic fibers are drawn. These pairs of rolls are geared to rotate at progressively faster speeds so that as the slivers pass from nip to nip, the individual fibers are drafted and stretched out to substantially their full length while being simultaneously aligned in side-by-side parallel arrangement to form a very thin, tenuous 'web. The drafting rolls are necessarily quite small in diameter because of the short length of the staple synthetic fibers customarily used. In the common staple grades available for synthetic fibers, lengths generally average about 2% inches, with a range of about 2 inches to about 2 /2 inches. To handle such fibers satisfactorily, the diameter of the rolls should be between 2 inches and 2% inches whereby the span between nips of paired rolls can be about 2 /2 inches. Smaller diameters may cause undesirable wrapping and fiber build-up on the roll, while larger diameters do 3,7 l 3 ,933 Patented .Fan. 30, 1973 not draft the fibers uniformly because the span between successive nips is excessive with respect to fiber length. The operation of small diameter rolls are no problem in narrow draw frames. It was found however, that as the width of the draw frame was increased in an attempt to provide wider webs more suitable for commercial application, the necessary limitation on diameter of the drafting rolls imposed by the described fiber length limitation, placed a corresponding limitation on the length of a roll which could be used. The longer rolls with this imposed diameter limitation were relatively more flexible and as a result the pressure exerted in the nip of a pair of drafting rolls varied transversely from end to end. This lack of uniformity in pressure prevented accurate fiber control in drafting, and as a result created variances in the thickness, density, and alignment of the issuing fiber web. It was clear that such undesirable flexing could be relieved somewhat by increasing roll diameter, but as noted previously, since the length of individual fibers in the fibrous material limits the maximum diameter of the rolls, such as obvious solution was impractical. It was found that supporting backup rolls would alleviate the problem in part, but even when such rolls were used the practical width of the web product which could be obtained was still limited. Webs up to 60 inches wide were produced satisfactorily with such arrangements, but still wider webs using the above described fiber lengths are now in demand. The present invention makes it possible to make high quality webs up to almost any width desired, while avoiding the mechanical problems described above.

Accordingly it is an object of this invention to provide a method and apparatus for producing extra wide non-woven webs from juxtaposed arrays of highly-drafted and aligned fibers.

Another object is to provide an arrangement whereby light-weight webs of highly-drafted and aligned staple length synthetic fibers are kept under tension while being aligned in side-by-side arrangement.

Still another object is to provide an arrangement in which light-weight webs of highly-drafted and aligned fibers are kept under tension while being superposed and laminated to each other to make plied-up-webs.

SUMMARY OF THE INVENTION The invention comprises an arrangement utilizing at least two separate draw frames to process juxtaposed slivers of staple length synthetic fibers into thin webs of highly-drafted and aligned fibers, and subsequently depositing these webs on a moving take-away belt in a manner to preserve the drafted and aligned nature of the fibers. The deposited Webs may be joined along their edges to provide much wider webs of uniform thickness, or the webs may be deposited on top of one another to form laminates. The important feature is that the webs issuing from the frames be deposited on the take-away belt under tension. The tension maintains the fibers in their aligned and highly drafted condition during transfer, until they are bonded by known means into a selfsustaining web form.

In this invention, individual drawn webs are kept under tension through the utilization of a particular angular relationship established between the plane of the web as it issues from the draw frame, and the plane of a receiving belt on which the web is deposited. The highly-drafted web, as it issues from each draw frame, is passed under a tensioning bar or rod and is then deposited on a moving receiving belt at a point where the belt passes around a turning roll. The axis of the tensioning bar is parallel to the axis of the guide roll. The tensioning bar is positioned sufliciently below an imaginary extension of the plane formed by the belt after it passes around the turning roll, so that such extension intercepts at least the lower surface of the tensioning bar. Preferably, the bar is arranged so that the angle of the plane of the drafted web at the point where it is deposited on the belt is several degrees less than the plane of the receiving belt. In past arrange ments where only a single draw frame is involved, as in the production of narrow webs, means for maintaining tension in the drafted web during transfer is of course quite simple, in that the belt need merely be passed around a turning roll positioned near the discharge end of the draw frame, and disposed in a manner to carry the deposited web away from the draw frame on a substantially horizontal plane and at a speed slightly faster than the discharge speed. However, when it is desired to produce webs which are wider than it is now possible to obtain with a single draw frame because of the drafting roll diameter limitations previously described above, additional draw frames must be provided and the posi tioning arrangement of the receiving belt to the draw frames adjusted accordingly. Since the space required for the driving and mounting mechanism of the drafting rolls dictates against aligning the draw frames in a side-by-side arrangement such that the edges of the issuing webs engage each other without an intervening gap, it is necessary for one draw frame to be on a different level than its neighbor. Therefore, in order to service more than one draw frame, the receiving belt requires a special orientation. Instead of having the belt pass around a single turning roll with the top run of the belt leaving the roll on a horizontal plane, the belt is arranged to leave a first turning roll at an angle inclined upwardly from the horizontal. The belt is then arranged to pass over a second turning roll and resume its travel in a horizontal plane. A first draw frame is arranged to deposit its web under tension on the upwardly-inclined belt at a point where the belt is tangent to the turning roll. This is done by first passing the web as discharged from the draw frame under a tensioning bar With its lower edge disposed slightly beneath an imaginary plane extending from the plane of the inclined receiving belt, then directing the web upward again to press against the belt surface causing the web to be deposited on said belt under tension.

The second draw frame is disposed above the first draw frame and adjacent the second turning roll in a similar manner, so that the drawn web passes under a tensioning bar disposed slightly beneath an imaginary plane extending from the plane of the horizontal run of the belt before being deposited on the belt.

As indicated previously, in order to be able to deposit the web issuing from the second draw frame onto the belt so that one of its edges is in juxtaposed relation to the edge of the web previously deposited on the belt from the first draw frame, the second frame must be disposed on a different level from the first frame to allow space for the roll drive and supporting mechanism. To permit such an arrangement of the draw frames, the receiving belt is inclined upwardly from the first turning roll, and the second frame is disposed above and forward of the first frame adjacent the inclined belt and tilted at an angle complementary to the upwardly-inclined angle of the belt. Transfer of drawn web to belt from the second frame then is possible in the same manner as transfer of drawn web to belt from the first frame.

When laminated products made of plied-up webs are desired, rather than the extra wide fabrics described above, such laminated products may be obtained by utilizing a similar arrangement but having the second frame deposit its web directly on top of the previously deposited web from the first frame.

Prior to accepting the web of highly-drafted fibers, the receiving belt is usually printed with an adhesive into which the fibers are embedded in their fully extended form. The adhesive is subsequently set or cured to bind th i e s a d fa m a selfp rt bh b y be subsequently stripped from the belt, which has previously been treated with a release agent, and utilized in that form for additional processing, or the belt itself may comprise a material such as light-weight tissue or creped wadding which eventually becomes an integral part of the product, as more particularly described and set forth in applicants U.S. Pat. 3,327,708.

These and other features, objects and advantages attendant the subject invention will become apparent by reference to the following specification and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 is a schematic side elevation of one arrangement of an apparatus for carrying out the invention.

FIG. 2 is an enlargement of a portion of the arrangement shown in FIG. 1, illustrating in more detail the angular disposition of certain elements.

FIG. 3 is a diagrammatic perspective view of another embodiment of an apparatus suitable for carrying out the process of this invention.

Like reference numerals designate like parts in the several views.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIGS. 1 and 2 of the drawings, there will be found a schematic illustration of an apparatus for carrying out the method of this invention. 11 represents a first draw frame comprising a plurality of upper and lower drafting rolls designated 17 and 18 respectively and a depression rod 19. 12 represents a second draw frame comprising a plurality of upper and lower drafting rolls designated 20 and 21 respectively and a depression rod 22. 14 is a receiving or take-away belt which moves in the direction shown around first turning roll 15 to form an inclined run 14a and then around second turning roll 16 to return to a horizontal run 1411. Belt 14 may be driven by means of one of the turning rolls shown, or by means located elsewhere, and travels at a speed slightly in excess of the speed of discharge web 25. 23 and 23a each represent an array of juxtaposed slivers being fed to draw frames 11 and 12 respectively. 25 and 25a each represent a highly-drafted web of aligned fibers issuing from draw frames 11 and 12 respectively. Broken line 27 represents an extension of the plane which belt 14 assumes on run 14a after passing around turning roll 15. Broken line 28 represents an extension of the plane of web 25 after passing around depression rod 19. 27a and 28a represent similar planes for the belt and web respectively after passing around roll 16 and rod 22 respectively.

In operation, arrays of continuous juxtaposed slivers 23 and 23a are drafted by passing them through the successive nips of their respective draw frames 11 and 12 to produce thin webs 25 and 25a of highly-drafted and aligned fibers. After discharge from draw frame 11, web 25 passes under depression rod 19 which maintains the web under tension. Web 25 then is directed upward to be deposited on belt 14a at a point slightly preceding the point of tangency 26 between belt 14a and roll 15 and indicated by radial line 29.

It is important to maintain the fibers under tension at all times after drafting and during transfer. When rod 19 depresses web 25 out of its original plane and below the plane of belt 14a, web 25 is caused to turn upward in a new plane designated 28. The depression of web 25 by rod 19 acts to hold the fibers in the web 25 continuously under tension. Belt 14 must, of course, travel at a speed slightly faster than the speed of issuing web 25 to maintain this tension. The tension maintains frictional engagement between adjacent fibers so that these fibers are retained in their highly-drafted and aligned form, whereby they remain substantially fully extended and parallel to.

each other. In order to insure that tension is maintained in the drafted fiber web during the transfer from tension rod 19 to belt 14a, the plane 28 of web 25 must be maintained angularly disposed with respect to the plane 27 of upwardly inclined belt 14a so that the web exerts a slight positive pressure against the belt surface. As shown in the drawings, belt 14a, after passing around roll 15 is inclined at an angle of about 25 The plane of web 25 after passing around rod 19 is angularly disposed at about below the plane of belt 14a at the point of tangency 2b.

The angularity between the web and belt 14a at the A point of deposition may be adjusted for best running conditions. It is important however for plane 28 to be angularly disposed below plane 27 in the attitude shown or web 25 will not exert sufficient pressure against belt 14a to be maintained under tension and the fibers will tend to become misaligned.

The operation of the second draw frame 12 is similar to that of the first draw frame. After discharge from draw frame 12, the highly-drafted fiber web 25a passes under depression rod 22 and is deposited on horizontal run 141) of the receiving belt. Frame 12 is disposed at an angle of about 25 to the plane of receiving belt run 14b. Rod 22 depresses web 25a out of its original plane and below the plane of belt 14b and causes web 25a to turn upward into a new plane designated 28a and at this angle is deposited on belt 14b at the point where belt 14b passes around turning roll 1-6. Plane 28a is angularly disposed at about 5 below the plane of belt 14b at its point of tangency with turning roll 16. The angular disposition of web 25a around roll 22 and with respect to its point of deposit on receiving belt 141) and the speed of the belt, provides the drafted and aligned fibers with the necessary tension.

As shown in FIG. 3 the second draw frame 12, in addition to being located above first draw frame 11, is offset to the near side of draw frame 11 so that far edge of web 25a meets the near edge of web 25 after being deposited on belt at run 14b. The arrangement of draw frame 12 with respect to the belt at 14b and roll 16 is similar to the arrangement of draw frame 11 with respect to the belt at 140. Since the belt at 14b diverges at about 25 from the belt at 14a, the draw frame 12 is also tilted in the same direction at about 25. The angular relationship of draw frame 12 and web 25a to the planes 27a and 28a is similar to that for draw frame 11 and web 25 to planes 27 and 28.

In addition to draw frames 11 and 12, a third draw frame 13 is shown in FIG. 3. Draw frame 13 has the usual upper and lower drafting rolls 30 and 31 and a depression bar 32. Web 25b leaving draw frame 13 is kept under tension and angularly disposed with respect to belt 14b in the same manner as web 2511. As shown, the third draw frame 13 is offset to the far side of the first frame 11 so that the near edge of web 25b meets the far edge of web 25. This arrangement is used when webs wider than can be produced with two draw [frames are required. The resulting product comprises a single wide web made up of separately deposited webs 25a, 25 and 25b reading from right to left. It will readily be seen that additional draw frames may be added alternately at the bottom and top so that a still wider web of almost indefinite width may be fabricated.

It is understood that prior to passing around roll 15, belt 14 has printed on its surface a pattern of adhesive to which the fibers in webs 25, 25a and 25b adhere as they are deposited. The adhesive serves two purposes. First, it grips the fibers firmly as the angular arrangement of the web and belt presses the fibers therein. Second, the adhesive acts as a permanent binder, after it is subsequently set or cured, to hold the fibers fully-extended in their tensioned alignment.

When the belt is treated with a release agent and used merely as a carrier for the adhesive, the bonded fiber web is subsequently stripped therefrom, and the finished web comprises only binder and fiber. An alternative arrangement is to substitute for belt 14 a light-weight sheet of creped tissue such as cellulose wadding. This tissue is printed with the adhesive and after the fibrous web is applied and pressed therein, and the adhesive cured, the tissues become an integral part of the resulting sheet.

in adjusting the apparatus care should be taken to see that the depression rod cooperating with the upper draw frame is disposed sufliciently high above the previously deposited drawn web so that it does not touch the previously deposited web or interfere with its fiber alignment. The speed of the take-away belt should be regulated so that it exerts enough tension on the drafted web to maintain smooth alignment of the fibers. If the speed is excessive, the fiber-to-fiber tenacity will be destroyed and the fibers will pull apart in uncontrolled, non-uniform sections. When fibers of 2 inches to 2% inches are used, the length of draw between the last nip of the draw frame and the depression rod may be as much as 8 inches depending upon the weight and thickness of the drawn web. The draw between depression rod and take-away belt may vary from 4 inches to 6 inches. It has been found that the fiber-to-fiber tenacity of the web is sufficient to keep the web intact over these seemingly excessive draw lengths as long as slight tension is maintained.

While the angular disposition of the web to belt is shown as 5 in the drawings, it will be understood that this angularity may be varied to suit the best running conditions as long as the angularity of the web [falls below the plane of the receiving belt. The take-away angles of the receiving belt may also be varied from the 25 shown to suit mechanical design requirements. It will be seen further that draw frames may be employed at three different levels if the first take-away angle is set at about 50, followed by a second belt angle of about 25 before returning the belt to its horizontal configuration.

While several specific embodiments of the inventive concept have been set forth above, it is understood that the invention is not to be construed as limited thereby, and that suitable changes, modifications, and variations may be made without departing from the spirit and scope of the invention as defined in the appended claims.

I claim as my invention:

1. A method for joining together multiple webs of highly drafted and aligned staple length fibers which comprises the steps of (a) discharging one of said webs as a continuous fiat sheet of juxtaposed fibers from the final nip of a first drafting device,

(b) guiding said web out of its original plane and at least partially around a turning bar and then directing said web upwardly,

(c) depositing said web in its upward run onto an upwardly inclined 'belt at an angular relationship in which the plane of said belt is such that said belt intercepts said upwardly directed web,

(d) discharging another of said webs as a continuous flat sheet of juxtaposed fibers from the final nip of a second drafting device located above said first drafting device,

(e) guiding said second web out of its original plane and at least partially around a turning bar and then directing said web upwardly,

(f) depositing said web in its upward run onto said belt and in contact with said first web at an angular relationship in which the plane of said belt is such that said belt intercepts said upwardly directed second web,

(g) maintaining said webs under tension by drawing said webs away from said final hips and partially around said turning bars at a speed slightly in excess of the speed with which said webs are being discharged from said hips, and

(h) bonding the fibers in said webs to each other with an adhesive carried on said belt to form a self-sustaining fabric.

2. The method of claim 1 in which the surface of said belt is treated with a release agent on which the adhesive is applied prior to said webs being deposited thereon and the adhesively bonded fiber Web is subsequently stripped from the surface of said belt.

3. The method of claim 1 in which the surface of said belt is a sheet of creped cellulose wadding on which the adhesive is applied prior to said webs being deposited thereon and, after the adhesive is cured, the wadding becomes a part of said self-sustaining fabric.

4. The method of claim 1 in which said second web is deposited on said belt in juxtaposed position with one edge of said first web abutting one edge of said second web.

5. The method of claim 1 in which said second web is deposited on top of said first web.

6. The method of claim 1 in which an additional web is deposited in juxtaposed position with said second web in the same method as said first web.

7. The method of claim 1 in which additional webs are deposited in juxtaposed positions on said belt in the same angular relationship as said first and second webs alternately.

References Cited UNITED STATES PATENTS 3,215,577 11/1965 Sinnott 156166 3,367,814 2/1968 Weiner et al. 156-166 WILLIAM A. POWELL, Primary Examiner I. J. BELL, Assistant Examiner US. Cl. X.R. 

